Current battery-based vehicular propulsion systems are in the form of a battery pack made up of numerous battery modules each of which is in turn made up of one or more battery cells that may deliver electric current for motive power for an automobile. In the present context, the term “motive power” describes a battery pack capable of providing more than mere starting power for another power source (such as an internal combustion engine); it includes battery packs capable of providing sustained power sufficient to propel a vehicle in a manner consistent with that for which it was designed.
An example of this type of system is shown in FIG. 1. A vehicular propulsion system in the form of a battery pack 1 employing numerous battery modules 10 is shown in a partially-exploded view. Depending on the power output desired, numerous battery modules 10 may be combined as a group or section 100; such may be aligned to be supported by a common tray 200 that can also act as support for coolant hoses 300 that can be used in configurations where supplemental cooling may be desired. In addition to providing support for the numerous battery modules 10, tray 200 and a bulkhead 400 may support other modules, such as a voltage, current and temperature measuring module 500. Placement of individual battery cells 35 within one of battery modules 10 is shown, as is the covering thereof by a sub-module 600. In one typical example, battery pack 1 may include about two hundred individual battery cells 35. Such a system is described in U.S. Publication 2012/0258337 A1, entitled Battery Thermal Interfaces with Microencapsulated Phase Change Materials for Enhanced Heat Exchange Properties, published Oct. 11, 2012, which is incorporated herein by reference.
A battery thermal system with interlocking structural components is shown in FIGS. 2A and 2B. The battery thermal system includes a module having a module base 55 and a heat sink 60. The module base 55 contains the battery cells 35 and solid fin assemblies 70, which are arranged along the edges of the battery cells 35. The solid fin assembly 70 includes a pair of solid fins 85 surrounded by an expansion unit 90, and inserted into a foot 95. The design of the solid fin assembly 70 allows deformation and therefore cell tolerance and expansion management. The feet 95 have interlocking profiles 110, 115 on opposite ends. The profile on one foot interlocks with the opposing profile on the next foot. As the battery cells 35 and solid fin assemblies 70 are arranged, the interlocking profiles 110, 115 on the feet 95 interlock with each other, forming a surface onto which the heat sink 60 can be easily attached. The solid fin assemblies 70 conduct heat generated in the battery cells 35 to the heat sinks 60, which are mounted on at least one side of the module base 55 (typically both sides). The module base 55 can be held together by end plates 75 and brackets 80, if desired. The feet 95 are in contact with the heat sink 60. The contact can be direct such that the feet 95 touch the heat sink 60, or indirect in which there is a layer of material between the feet 95 and the heat sink 60.
The design of the solid fin assembly 70 due to the flexible joints formed along the adjacently joined feet 95 allows deformation due to the tower of stacked solid fin assemblies that may bend along its length, forming a banana or snake shape. Such a system is described in U.S. Publication 2012/0107649 A1, entitled Battery Thermal System with Interlocking Structure Components, published May 3, 2012, which is incorporated herein by reference. While such a system works well for its intended purpose, the present inventors have determined that this flexing tendency can cause loss of thermal contact and related reduction in the thermal performance of the battery thermal system.